Airing and venting valves with seating seals are known, for example of the type whereby an actual float on a seal seating provides the sealing effect. Documents DE 299 05 743 U1 and DE 299 18 722 U1 also disclose airing and venting valves comprising a valve body, a seal cup and a cup seal disposed in between, and the proposed valve body is of a frustoconical design tapering towards the bottom, whilst the seal cup has a cylindrical internal shape. The disadvantages of these known valves are that their venting power is limited by the restricted end-to-end cross-section of the radially disposed valve body orifices and the cup seal is more susceptible to forces which could tear it off in the closed position, which necessarily requires the use of use heavier floats which therefore have a poorer buoyancy. In order to overcome these problems, the floats must be made bigger in order to create the ideal lifting and gravitational forces, which in turn leads to the problem of having to make the valves bigger.